Cooley played in 16 games with the Jazz last season after being called up from the NBA Developmental League. He averaged 1.7 points and 1.6 rebounds. Cooley's fate with the team seemed to be decided when 7-foot center Jeff Withey signed a multi-year free agent deal in August. The 6-9, 260-pounder was in his second NBA season.
O'Brien was signed as an undrafted rookie Aug. 28 and played in one preseason game with the Jazz.
The Jazz roster now stands at 18.